Automatic trip device



April 27, 1965 ZUBATY 3,180,953

AUTOMATIC TRIP DEVICE Filed Feb. 19, 1962 4 Sheets-Sheet 1 April 27, 1965 M. v. ZUBATY 3,180,953

AUTOMATIC TRIP DEVICE Filed Feb. 19, 1962 4 Sheets-Sheet 2 M. v. ZUBATY' April 27, 1965 AUTOMATIC TRIP DEVICE Filed Feb. 19, 1962 4 Sheets-Sheet 3 M. V. ZUBATY April 27, 1965 AUTOMATIC TRIP DEVICE 4 Sheets-Sheet 4 Filed Feb. 19, 1962 \\I m Q. Po \hw R h WE sasasss AUTOMATiC TKP DEVICE Martin V. Zubaty, Philadelphia, Pa, assignor to I-T-=E Circuit Breaker Company, Philadelphia, Pa, a corporation of Pennsylvania Filed Feb. 19, 1962, Ser. No. 174,124 14 Claims. (El. Mill-45%) The instant invention relates to circuit breakers in general and more particularly to a novel construction for an automatic trip device with special emphasis being placed upon the construction of the magnetic or instantaneous trip portion thereof.

In conventional molded case circuitbreakers the instantaneous tripping means often comprises a magnet and an armature whose rotational bearings are placed in the circuitbreaker base and secured by the'cover. The armature is held against a stop in the base by an extension spring. Thus, the magnetic gap varies with tolerances of molded parts which are subject to extreme variations. As a result, desired tripping values are very dificult to obtain.

In other prior art constructions the magnet is mounted to the thermal means bimetal and the armature is placed frce between the base and cover and held in the end position by an extension spring. With the latter arrangement, calibration varies with the adjustment of the thermal means and as a result it is very difiicult to obtain the desired instantaneous trip setting.

The instant invention overcomes the disadvantages of the prior art by providing a construction in which the pole piece of the magnet and the armature are both mounted to a retainer clip. The clip is constructed of non-magnetic sheet material which is very readily and inexpensively manufactured to extremely close tolerances. The energizing turn for the magnet is provided by the bimetal heater which is mounted remote from the armature and is mounted such that adjustment thereof will not affect the spacing between the armature and pole faces.

Accordingly, a primary object or" the instant invention is to provide a circuit breaker having a novel instantaneous tripdevice which is inexpensive to construct and is easy to calibrate.

Another object is to provide an automatic trip device of this type in which a spring retainer element is utilized to assemble themagnet and armature without any'additional fastening means being required.

Still another object is to provide an automatic trip deice which is extremelycompact.

A further object is to provide an instantaneous trip device in which one-or more fiat spring elements, interposed between the armature and magnet, are utilized for calibration purposes.

These as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a plan view of a circuit breaker including the device of the instant invention.

FIGURE 2 is a cross-section taken through line 2-2 of FlGURE 1 looking in the direction of arrows 2--2.

FiGURE 3 is an exploded perspective of an automatic trip unit constructed in accordance with the teachings of the instant invention.

FIGURE 4 is a crosssection of the automatic trip unit taken through line l4 of FIGURE 5 looking in the direction of arrows 44.

FIGURES 5 and 6 are end views of the trip unit looking in the direction of arrows 55 and 66, respectively of FIGURE 4.

FIGURE 7 is a cross-section taken through line 77 of FIGURE 4 looking in the direction of arrows 77.

FIGURE 8 is a cross-section taken through line 88 of FIGURE 7 looking in the direction of arrows 83.

United States Patent 0 3.180353 Patented Apr. 27, 1965 FIGURE 9 is a plan view illustrating the manner in which the instantaneous trip means biasing spring engages the armature.

Now referring to the figures. Circuit breaker 15 is provided with a molded housing comprising base 16 and removable cover 17. Base 16 is divided into three longitudinal compartments by partitions 18, 19. The center compartment houses contact operating mechanism 20 of a type well known to the art which is effective to simultaneously operate cooperating contacts 21, 22 of both circuit breaker poles into and out of engagement.

Circuit breaker 15 is a two pole device with the current carrying elements of the respective poles being housed in the outer compartments of base 16. The current carrying elements as well as the automatic trip device of each pole are the same. The current path for each pole comprises terminal strap 23, stationary contact 22, movable contact 21, movable contact arm element 24, flexible braid 25, strap 26, bimetal heater element 30 to terminal strap 31.

Movable contact arm element 24 is pivotally mounted at 32 to contact arm element 33 with contact pressure spring 34 being interposed between elements 24- and 33 to provide contact pressure. Elements 33 of both poles are fixedly secured to cross bar 35 which is operated by mechanism 2% to bring about simultaneous opening and closing of contacts 21, 22 of both poles. Circuit breaker 15 also includes common tripper bar 36 biased to latching position (arrow A, FIGURE 2) in a manner well known to the art.

in order to bring about automatictripping of circuit breaker 15, each of the poles is provided with an automatic trip unit 4t) including bimetal 39 and armature 38 which is attracted to the pole piece 37 of an electro-magnet. So-called instantaneous tripping takes place when armature 33 is attracted by pole piece 37 and moves in the direction of arrow B (FIGURE 2) and in so doing engages tripper bar extension 41, thereby rotating tripper bar 36 in the direction opposite to the direction of arrow A. So-called time delayed tripping takes place when the upper or free end of bimetal 39 moves in the direction of arrow C (FIGURE 2) thereby engaging tripper bar extension 42 to operate tripper bar 36 in a direction opposite to the direction indicated by arrow A.

Bimetal heater element $4 is of generally rectangular shape having elongated oppositesides 43, 44. The upper ends of sides lfi, 44 are bridged by side 45 while side 46 extends from the lower end of side 43 but stops short of side 44. Side as is provided with clearance aperture 47 which receives mounting screw 48. The lower end of side 4 is provided with leg 49 extending away from side 43. Leg .9 is provided with clearance aperture 51' which receives mounting screw 51.

As clearly seen in FIGURES 3 and 6, side 44 is considerably narrower than sides 43, 45 and 4-6 so that most of the heating takes place at side 44. The lower end of bimetal 39 is secured to the downward extension 52., of side 44, which is formed from extension 4h. The threads of adjusting screw 53 are mated with the threads of aperture 54 through side 43. End 55 of screw 53 is provided with a suitably formed recess to receive an ad- 'justing tool such as an Allen wrench'while the other end of screw 53 is provided with a portion 56 of reduced cross section having an enlargement 57 at the free end thereof. Shoulder 58, adjacent to portion 56, abuts the inner surface of side 44 with portion 56 extending through clearance aperture 59 of side 44 and spring retainer 69 being interposed between enlargement 57 and the outside surface of side 44.

As adjusting screW 53 is rotated clockwise, a force is directed to increase the spacing between the central portions of walls 43 and 44. This re-positions the extension delay tripping interval for circuit breaker 15. It is noted that end 55 of adjusting screw 53 is made accessible with i the cover 17 of circuit breaker 15 in place merely by removing cover strip 62 which is disposed within slotted formations of base 16.

Pole piece 37 is a generally U-shaped member provided with pole faces 64, 65 which lie in a common plane. Pole piece 37 is nested .within U-shaped retainer slip 66 with outward projections 67 of the pole piece U-arms disposed within apertures 68 in the U-arms of retainer clip 66. The web of pole piece 37 is provided with clearance aperture 69 while the web of the retainer clip 66 is provided with clearance aperture 70. Apertures 69 and 70 are aligned with aperture 47 of heater side 46 so that screw 48 extends through all three elements and constitutes a common fastening means.

The U-arms ofretainer element 66 each include portions extending beyond pole faces 64, 65. These portions are provided with aligned apertures 71,72 which receive outboard extensions 73, '74, respectively of armature 36 thereby defining a pivotal axis for armature 38. These portions of retainer clip 66 also include enlarged apertures 75, 76 which receive outboard extensions 77, 78, respectively, of armature 33. Apertures 75, 76 are considerably larger than extensions 77, 78 thereby permitting armature 38 to pivot toward and away from pole faces 64, 65.

Each of the U-arms of pole piece 37 is provided with an under cut portion 79 while armature 38 is provided with two sets of indentations 90. Somewhat V-shaped compression leaf spring 91 is interposed between pole piece 37 and armature 38 thereby urging armature 38 away from pole faces 64, 65. Each end of spring 91 is notched to provide a pair of closely spaced tips 92. Tips 92 at one end of spring 91 are received by one of the sets of notches 90 while the tips 92 at the other end of spring 91 are disposed on opposite sides of under cut 79 thereby ecurely positioning spring 91. The amount of force urging armature 38 away from pole faces 64, 65 is regulated by utilizing either a single spring 91 or two separate springs 91 located at opposite sides of armature 33. Further, this force is regulated by the characteristics and dimensions of the spring material. It is noted that retainer clip 66 is counstructed of non-magnetic resilient sheet material so that no additional fastening means are required to secure pole piece 37, armature 38 and re tainer clip 66 together as a unit. Further, the mounting of pressure spring 91 is extremely simple and does not require the permanent deformation of any element.

Although preferred embodiments of this novel invention are described herein, many variations and modifications will now be apparent to those skilled in the art and, therefore, it is preferred that this invention be limited not by the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An automatic trip device for a circuit breaker, said device comprising an electro-magnet having a U-shaped pole piece including space-separated arms, a connecting web and pole faces lying in a common plane perpendicular to said U-forming arms and web, a U-shaped retainer element, said retainer element including space separated arms, said pole piece nested within said retainer element with the webs of the nested members adjacent to each other, said retainer element arms each including a portion extending beyond said U-shaped pole piece, and perpendicular to said pole faces; the extending portion of one of said arms having afirst aperture located adjacent a first end of one of said pole faces, the extending portion of the other of said arms having a second aperture located adjacent a first end of the other of said pole faces; said first and second apertures in alignment and defining a pivotal axis across said pole faces at their first end; an armature for said electro-magnet; said armature including pivot means extending into said first and second apertures, for pivotally mounting said armature to said extending portions, such that the pivoted end of said armature extends across said pole faces at the first end thereof; spring means for urging said armature about said pivotal axis in a direction away'from said pole faces.

2. The automatic trip device of claim 1 in which the retainer element comprises a member constructed of nonmagnetic spring material. 1

3. The automatic trip device of claim 1 in spring means comprises an elongated leaf member one end of'which bears against an arm of said U-shaped pole piece and the other end of which bears against said armature.

4. The automatic trip device of claim 1 in which the armature'is provided with limit projections, said portions of said retainer element each having apertures within .which said projections are disposed whereby movement of said armature away from said pole faces is limited to a predetermined position.

5. The automatic trip device of claim 1 in which the U-arms of the retainer element are provided with holes, the U-arrns of the pole piece having projections disposed within said holes whereby said pole piece and said retainer element are operatively positioned as an integrally maintained unit. 7

6. The automatic trip device of claim 1 in which there are aligned clearance apertures in the webs of said retainer element and said pole piece, an elongated bimetal extending between'the U-arms of the pole piece, and a member to which one end of the bimetal is mounted with the other end of the bimetal being free to deflect upon heating of the bimetal, said member including an aperture aligned with said aligned apertures whereby a common fastening member is useable for securing said bimetal and said pole piece within a circuit breaker housing.

7. A multi-phase circuit breaker including a pair of cooperating contacts for each phase; a mechanism for simultaneously operating said contacts of all phases be tween an engaged and a disengaged position; a common tripper bar which when operated to a trip position enables said mechanism to automatically operate said pair of contacts of all phases to said disengaged position; a

magnetic trip device for each phase of said circuit breaker; each of said devices comprising an electro-magnet having a U-shaped pole piece including space-separated arms, a connecting web and pole faces lying in a common plane perpendicular to said U-forming arms and-web, a U-shaped retainer element,said retainer element including space separated arms, said pole piece nested within said retainer element with the webs of the nested members adjacent to each othensaid retainer element arms each including a portion extending beyond said U-shaped pole piece, and perpendicular to said pole faces; the extending portion of one of said arms having a first aperture located adjacent a first end of one of said pole faces, the extending portion of the other of said arms having a second aperture located adjacent a first end of the other of said pole faces; said first and second apertures in alignment and defining a pivotal axis across said pole faces at their first end; an armature for said electromagnet; said armature including pivot means extending into said first and second apertures, for pivotally mounting said armature to said extending portions, such that the pivoted end of said armature extends across said pole faces at the first end thereof; spring means for urging said armature about said pivotal axis in a direction away from said pole which the V faces; said armature being attracted by said electro-magnet and thereby moved about said axis toward said pole faces upon the occurrence of a predetermined overload condition, said armature in moving toward said pole faces operating said tripper bar to said trip position.

8. The circuit breaker of claim 7 in which there is a thermal trip device for each phase; each of said thermal trip devices comprising a bimetal which upon the occurrence of another predetermined overload condition will deflect sufiiciently to operate said tripper bar to said trip position, said thermal trip device also comprising a heater member for said bimetal, said heater member mounted between the arms of said pole piece and being operatively positioned so as to constitute an energizing turn therefor, said heater member being mounted in heat transferring relationship to said bimetal.

9. The circuit breaker of claim 8 is which the bimetal of each phase is fixedly secured to said heater member, a common fastening means securing said heater member and said pole piece to a base of said circuit breaker.

10. The circuit breaker of claim 7 in which each of the retainer elements comprises a member constructed of non-magnetic spring material.

11. The circuit breaker of claim 7 in which each of the spring means comprises an elongated leaf member one end of which bears against an arm of said U-shaped pole piece and the other end of which bears against said armature.

12. The circuit breaker of claim 7 in which each of the armatures is provided with limit projections, said portions of said retainer clement each having apertures Within which said projections are disposed whereby movement of said armature away from said pole faces is limited to a predetermined position.

13. The circuit breaker of claim 7 in which each of magnetic trip devices is constructed with the U-arms of the retainer element having holes, the U-arms of the pole piece having projections disposed within said holes whereby said pole piece and said retainer element are operatively positioned as an integrally maintained unit.

14. The circuit breaker of claim 7 in which each of the magnetic trip devices is constructed with aligned clearance apertures in the webs of said retainer element and said pole piece, an elongated bimetal extending between the U-arrns of the pole piece, a member to which one end of the bimetal is mounted with the other end of the bimetal being free to deflect upon heating of the bimetal, said member including an aperture aligned with said aligned apertures, a common fastening means extending through said last recited aperture and said aligned apertures for securing said bimetal and said pole piece to a housing for said circuit breaker.

References Cited by the Examiner UNITED STATES PATENTS 2,281,743 5/42 Brown 200-88 2,419,125 4/47 Dorfman et a1 20088 2,981,811 4/61 Steven 20088 ROBERT K. SCHAEFER, Acting Primary Examiner. 

1. AN AUTOMATIC TRIP DEVICE FOR A CIRCUIT BREAKER, SAID DEVICE COMPRISING AN ELECTRO-MAGNET HAVING A U-SHAPED POLE PIECE INCLUDING SPACE-SEPARATED ARMS, A CONNECTING WEB AND A POLE FACES LYING IN A COMMON PLANE PERPENDICULAR TO SAID U-FORMING ARMS AND WEB, A U-SHAPED RETAINER ELEMENT, SAID RETAINER ELEMENT INCLUDING SPACE SEPARATED ARMS, SAID POLE PIECE NESTED WITHIN SAID RETAINER ELEMENT WITH THE WEBS OF THE NESTED MEMBERS ADJACENT TO EACH OTHER, SAID RETAINER ELEMENT ARMS EACH INCLUDING A PORTION EXTENDING BEYOND SAID U-SHAPED POLE PIECE, AND PERPENDICULAR TO SAID POLE FACES; THE EXTENDING PORTION OF ONE OF SAID ARMS HAVING A FIRST APERTURE LOCATED ADJACENT A FIRST END OF SAID POLE FACES, THE EXTENDING PORTION OF THE OTHER OF SAID ARMS HAVING A SECOND APERTURE LOCATED ADJACENT A FIRST END OF THE OTHER OF SAID POLE FACES; SAID FIRST AND SECOND APERTURES IN ALIGNMENT AND DEFINING A PIVOTAL AXIS ACROSS SAID POLE FACES AT THEIR FIRST END; AN ARMATURE FOR SAID ELECTRO-MAGNET; SAID ARMATURE INCLUDING PIVOT MEANS EXTENDING INTO SAID FIRST AND SECOND APERTURES FOR PIVOTALLY MOUNTING SAID ARMATURE TO SAID EXTENDING PORTIONS, SUCH THAT THE PIVOTED END OF SAID ARMATURE EXTENDS ACROSS SAID POLE FACES AT THE FIRST END THEREOF; SPRING MEANS FOR URGING SAID ARMATURE ABOUT SAID PIVOTAL AXIS IN A DIRECTION AWAY FROM SAID POLE FACES. 